Method of producing a deposited catalyst for the polymerization of ethylene and copolymerization of ethylene with O-olefins

ABSTRACT

A method is proposed for producing a deposited catalyst for the polymerization of ethylene and copolymerization of ethylene with δ-olefins which involves the reaction of a solution of an organomagnesium compound of composition MgPh 2 .nMgCl 2 .mR 2  O (wherein n=0.37-0.7; m≧2, R 2  O is a simple ether, Ph is C 6  H 5 ) with a carbon tetrachloride, at a molar ratio of CCl 4  /Mg≧0.5 and a temperature of -20° to 60° C.

The invention relates to methods of producing catalysts for thepolymerization of ethylene and copolymerization of ethylene withδ-olefins, more specifically to deposited catalysts comprising atransition metal compound based on magnesium-containing carrier.

THE PRIOR ART

There is known a method of producing deposited ethylene polymerizationcatalysts comprising a transition metal compound (TICl₄, VCl₄, VOCl₃ ona carrier of the formula: Mg_(m) Cl_(n) C_(p) Hg (m=0.80-0.95,n=1.60-1.90, p=0.8-1.6, g=1.4-3.4) (SU 726702 A; SU 1400657 A) bydepositing transition metal compounds onto the carrier. In doing so, acarrier is formed by reacting metallic magnesium powder with alkylchloride in a hydrocarbon medium at a RCl/Mg molar ratio greater than 2.

The main disadvantage of catalysts produced by this method is anuncontrollable granulometric composition of a catalyst powder having awide catalyst particle size distribution varying from 1 to 100 microns.

As polymerization occurs, a polymer powder having a wide particle sizedistribution and relatively low bulk density (0.22-0.30 g/cm³) is formedon such a catalyst.

It is known from the prior art that substantial improvement in themethod performance can be achieved by producing a polymer powder havingnarrow particle size distribution and greater bulk density. To this end,polymerization catalysts having narrow particle size distribution andimproved morphology are used. In this case, different polymerizationtechnologies and different polymer application require catalysts havingdifferent particle size, e.g. 10-25 microns for suspensionpolymerization of ethylene and 25-50 microns for gas phasepolymerization.

A catalyst having narrow particle size distribution comprising magnesiumchloride as the carrier can be produced by reaction of a MgCl₂.3-i-C₈H₁₇ OH compound solution in a hydrocarbon diluent with TiCl₄ in thepresence of an electron donor compound such as ethyl benzoate, ethylanizate, and the like (see Japanese Application No. 59153511). Thecatalyst thus produced has a particle size of 5-15 microns and hasrather high activity (up to 35 kg/PE g per Ti.h.atm C₂ H₄) and allowsone to produce polyethylene powder having narrow granulometry and highbulk density.

The method of producing a catalyst is disadvantageous in that it iscarried out at low temperatures (up to minus 20° C.), large amounts ofliquid TiCl₄ are used as a reaction medium and a considerable amount ofhydrogen chloride liberate during synthesis of the catalyst. Besides,this method is used to produce catalysts having a particle size ofgreater than 15 microns.

There is known a method for the preparation of a catalyst by reaction ofa (RMgR'.nAlR"mD) with chlorohydrocarbon and by subsequent reaction ofthe resulting solid product (carrier) with titanium or vanadium halide(see FRG Patent N 326060 and French Patent N 2529207). The RMgR'organomagnesium compound includes (n-Bu) Mg(i-Bu) or (n-Bu)Mg(Oct)compounds soluble in hydrocarbons, and the chlorohydrocarbon compound ispreferably tert-BuCl.

The main disadvantage of the catalysts prepared by this method is thatthey are not sufficiently active.

DISCLOSURE OF THE INVENTION

The object of the claimed invention is to develop a method of producingcatalysts for the polymerization of ethylene and copolymerization ofethylene with δ-olefins. This method makes it possible to producepolymers having narrow and controllable particle size distribution andgreater bulk density and retaining high activity during suspension andgas phase polymerization of ethylene and copolymerization of ethylenewith δ-olefins.

This object can be attained by using the Mg(C₆ H₅)₂ nMgCl₂ mR₂ Oorganomagnesium compound (wherein C₆ H₅ is phenyl, n=0.37, m≧2, R₂ O isether, preferably dibutyl or diisoamyl ether) to prepare amagnesium-containing carrier for these catalysts. An organomagnesiumcompound is prepared by reacting magnesium powder with chlorobenzene inthe presence of ether, preferably dibutyl or dicsoamyl ether. Amagnesium containing carrier can be prepared by reacting a solution ofthe above-mentioned organomagnesium compound with carbon tetrachlorideat temperatures between -20° C. to 60° C. and a CCl₄ /Mg molar ratio ofequal or greater than 0.5. At this stage, a magnesium-containing carrierpowder is formed. This powder has the required particle size and narrowparticle size distribution in the form of a suspension in the solventused. Catalysts are prepared by subsequent treatment of amagnesium-containing carrier with a solution of TiCl_(n), VCl₄ or VOCl₃in a hydrocarbon solvent at a Ti(V)/Mg molar ratio of 0.2-1.0 and attemperatures between 20° C. and 100° C.

The main distinctive feature of the claimed method for the preparationof catalysts is using a Mg(C₆ H₅)₂. nMgCl₂.mR₂ O complex organomagnesiumcompound in solution form in chlorobenzene, ether R₂ O or mixtures ofchlorobenzene with ether, chlorobenzene with aliphatic or aromaticcompounds at the magnesium -containing carrier preparation stage.Chlorination of this compound with carbon tetrachloride at temperaturesbetween -20° C. and 60° C. and a CCl₄ /Mg molar ratio of equal orgreater than 0.5 gives a solid magnesium containing carrier powdersuspended in a hydrocarbon solvent. The carrier thus prepared has anarrow particle size ranging from 5 to 50 microns. The required particlesize of a carrier and respectively a catalyst in this range ispredetermined by the organomagnesium compound composition and theconditions under which an organomagnesium compound is reacted withcarbon tetrachloride. The resulting magnesium containing carrierincludes preferably magnesium dichloride (80-90 wt %), ether (7-15 wt%), and complex hydrocarbon products (1-5 wt %). A catalyst is preparedby subsequent treatment of the carrier with solution of titaniumtetrachloride TiCl₄ or vanadium chloride (VCl₄, VOCl₃) in a hydrocarbonsolvent.

The claimed method makes it possible to prepare highly active catalystshaving narrow particle size distribution for various applications andaccordingly various particle sizes. For example, as is evident from thepresent invention, one can produce catalysts with a particle size of5-10 microns and 10-25 microns for suspension polymerization of ethyleneand catalysts with a particle size of 20-50 microns for gas phasepolymerization of ethylene. As ethylene polymerization occurs,polyethylene having high bulk density (greater than 0.35 g/cm³) andnarrow particle size distribution (a SPAN value less than 1) is formedon this catalyst. The use of titanium chloride as an active component inthese catalysts gives polyethylene having narrow molecular weightdistribution which is defined by the MI₅ /MI₂ ratio of equal or greaterthan 3.1 (Examples 1-6 in the table), and the use of vanadium chlorideprovides polyethylene having wide molecular weight destribution (MI₅/MI₂ value is greater than 4, Examples 8 and 9 in the table). Activityof the resulting catalysts amounts to 140 kg polyethylene (PE)/gTi.h.atm C₂ H₄ or 20 kg PE/g V.h. atm C₂ H₄. Catalysts are used for thepolymerization of ethylene or copolymerization of ethylene withδ-olefins in combination with a aluminium trialkyl cocatalyst(preferably aluminium triisobutyl or aluminium triethyl). Polymerizationis carried out under suspension conditions at temperatures between 50°C. and 100° C. in a hydrocarbon solvent, (e.g. hexane or heptane) orunder gas phase conditions without a hydrocarbon diluent at temperaturesbetween 60° C. and 100° C. and at pressures ranging from 2 to 40 atm.The polymer molecular weight regulator is hydrogen in an amount of 5-50%by volume. During copolymerization of ethylene with δ-olefins,propylene, butene-1, hexene-1, 4-methylpentene-1 or other higherδ-olefins are used.

The essence of the present invention is illustrated by the followingexamples.

EXAMPLE 1

A. Preparation of an Organomagnesium Compound Solution

In a 11 glass reactor provided with a stirrer and a thermostating device29.2 g of magnesium powder (1.2 mole) are reacted with 450 ml ofchlorobenzene (4.4 mole) in the presence of 203 ml of dibutyl ether (1.2mole) and an activating agent which is essentially a solution of 0.05 gof iodine in 3 ml of butyl chloride. The reaction is carried out in anatmosphere of inert gas (nitrogen and argon) at a temperature between80° C. and 100° C. for 10 hours. On completion of the reaction, theresulting reaction mixture is allowed to settle and the liquid phase isseparated from the precipitate. The liquid phase is essentially aMgPh₂.0.49 MgCl₂.2(C₄ H₉)₂ O organomagnesium compound solution having aconcentration of 1.1 Mg mole/l .

B. Synthesis of a Carrier

100 ml of the resulting solution (0.11 Mg mole) are charged into areactor provided with a stirrer and 21.2 ml of CCl₄ solution in 42 ml ofheptane (0.22 CCl₄ mole) are dosed into the reactor at a temperature of20° C. for 1 hour. The reaction mixture is maintained at thistemperature, and after stirring for 60 minutes, the mother liquor isthen removed, and the precipitate thus formed is washed with heptanefour times in 100 ml portions at a temperature of 60 C to give 11.8 g oforganomagnesium carrier powder in the form of a slurry in heptane.

Preparation of a Catalyst

12.1 ml of TiCl₄ (TiCl₄ /Mg=1) are poured to the resultingmagnesium-containing carrier slurry in heptane, the reaction mixture isheated to 80° C. and maintained under stirring for 2 hours, the solidresidue is then allowed to settle and washed with heptane at atemperature of 60° C. four times in 100 ml portions, to give a depositedcatalyst containing 21.3 wt % titanium. The average particle size is 13microns.

Ethylene polymerization is carried out in a 0.7 l steel reactor providedwith a slirrer and a thermostating jacket. The solvent used in thepolymerization process includes a n-fexane (2.50 ml) and a Al(i-Bu)₃cocatalyst having a 5 mmole/l concentration. The polymerization iscarried out at a temperature of 80° C., an ethylene pressure of 3.5 atm.a hydrogen pressure of 1 atm for 1 hour. The ethylene polymerizationresults are summarized in the table. To carry out a test, 0.009 g of acatalyst is used to give 39 g of a polymer. The catalyst activity is 4.3kg PE/g catalyst per hour or 187 kg/g Ti per hour. The PE melt index(MI₅) at a load of 5 kg and a temperature of 190° C. is 6.7 g/10 min,and the index ratio at loads of 5 kg and 2.16 kg is 3.1.

The PE powder bulk density is 0.37 g/cm³, and the average PE particlesize as measured by screen analysis is 280 microns. The PE powder hasnarrow particle size distribution which is determined by the SPAN valuecalculated from the screen analysis data: SPAN=(d₉₀ -d₁₀) d₅₀ whereind₉₀, d₁₀ and d₅₀ are PE particle size corresponding to the integralcontent of particles in amounts of 90, 50 and 10 wt %, respectively. TheSPAn value for this example is 0.75.

EXAMPLE 2

An organomagnesium compound solution is prepared as in Example 1 exceptthat diisoamyl ether is used instead of dibutyl ether, and the reactionis carried out at temperatures between 80° C. and 130° C. to give aMgPh₂.0.37 MgCl₂.2DIIAI organomagnesium compound solution having a 0,93Mgmole/l concentration.

The carrier and the catalyst are synthesized as in Example 1 to give acatalyst having 3.0 wt % titanium and an average particle size of 13.6microns. The catalytic properties of the catalyst summarized in tabularform.

EXAMPLE 3

An organomagnesium compound solution is prepared as in Example 1 exceptthat 122 ml of chlorobenzene (1.1 mole) and 450 ml of dibutyl ether areused to give a MgPh₂.0.7 MgCl₂ nDBE organomagnesium compound solution indibutyl ether (wherein n is more than 2) having a 1.2 Mg mole/lconcentration.

A carrier is synthesized as follows. A carbon tetrachloride solution indibutyl ether (14 ml of CCl₄ in 28 ml of DBE) is added to 100 ml of anorganomagnesium compound solution (0,12 mole) at a temperature of 30° C.for 1,5 hours. Subsequent thermal treatment at 85° C. and washings areeffected as in Example 1.

The catalyst is produced as in Example 1, but the TiCl₄ /Mg molar ratiois 0.5 to give a catalyst containing 1.65 wt % titanium and having anoverage particle size of 14 microns. The catalyst properties of thecatalyst are summarized in tabular form.

EXAMPLE 4

An organomagnesium compound solution is synthesized as in Example 1. Acarrier is synthesized by adding a carbon tetrachloride solution inchlorobenzene (14 ml of CCl₄ in 14 ml of chlorobenzene) to 100 ml of anorganomagnesium compound solution at a temperature of minus 10° C. for1.5 hours. Subsequent operations of catalyst synthesis are carried outas in Example 1 to give a catalyst containing 2.5 wt % titanium andhaving an average particle size of 6 microns. The catalytic propertiesof the catalyst are summarized in tubular form.

EXAMPLE 5

An organomagnesium compound solution is prepared as in Example 1 exceptthat a chlorobenzene/toluene mixture (250 ml of chlorobenzene and 250 mlof toluene) is used instead of chlorobenzene to give a MgPh₂.0,6 MgCl₂.2 DBE organomagnesium compound solution having 0,85 Mg mole/lconcentration.

The carrier is synthesized as in Example 1 except that a CCl₄ solutionin toluene is used.

The catalyst is prepared as in Example 1 to give a solution containing5.3 wt % titanium and having an average particle size of 10 microns. Thecatalytic properties of the catalyst are summarized in tabular form.

EXAMPLE 6

An organomagnesium compound solution is synthesized as in Example 1.

A ClC₄ solution in DBE (14 ml of CCl₄ in 28 ml of DBE) is added to 100ml of an organomagnesium compound solution having 1.1 Mg mole/lconcentration under stirring at 36° C. for 40 minutes. On completion ofaddition, the temperature is raised to80° C. and the reaction mixture ismaintained at the given temperature and stirred for 1 hour, the motherliquor is then removed and the carrier is washed three times with 150 mlof n-hexane at 50°-60° C.

13 ml of TiCl₄ (TiCl₄ /Mg=1) is added by portions to the resultingcarrier in n-hexane at 20° C., the reaction mixture is heated to 60° C.and maintained under stirring for 1.5 hours. The catalyst is washed atthe given temperature six times with 150 ml of n-hexane to give acatalyst containing 2.0 wt % titanium having an average particle size of18.8 microns.

The catalyst properties of the catalyst are summerized in tabular form.

EXAMPLE 7

An organomagnesium compound solution is synthesized as in Example 2.

Carrier synthesis is carried out as in Example 6 except that theorganomagnesium compound is reacted with CCl₄ at a temperature of 50°C., and the CCl₄ /Mg ratio is 3.

Catalyst synthesis is carried out as in Example 6. The resultingcatalyst contains 1.7 wt % titanium and has an average particle size of38 microns. The catalytic properties of the catalyst are summarized intabular form.

EXAMPLE 8

An organomagnesium compound solution is synthesized as in Example 1.

Carrier synthesis is carried out as in Example 6 except that theorganomagnesium compound is reacted with CCl₄ at a temperature of 38° C.The resulting carrier is treated with a solution at 40° C. for 2 hoursand then washed four times with 100 ml of n-hexane.

Catalyst synthesis is carried out by treatment of the carrier at 40° C.for 1 hour with a VOCl₃ solution in CCl₄ (2 ml of the solution havingVOCl₃ / 1.6 mole/ml concentration. The catalyst is washed two times with70 ml n-hexane. The resulting catalyst contains 2.3 wt % vanadium andhas an average particle size of 20 microns. The catalytic properties ofthe catalyst are summerized in tabular form.

EXAMPLE 9

An organomagnesium compound solution is synthesized as in Example 2.

Carrier synthesis is carried as in Example 8 except that theorganomagnesium compound is reacted with CCl₄ at a temperature of 50° C.

Subsequent operations of synthesis of the carrier and the catalyst arecarried out as in Example 8 except that vanadium tetrachloride is usedinstead of vanadium oxytrichloride to give a catalyst which contains 2.1wt % vanadium and has an average particle size of 37 microns. Thecatalyst properties of the catalyst are summarized in tabular form.

EXAMPLE 10

The catalyst produced in Example 4 is used for the preparation ofpolyethylene powder having superhigh molecular weight. Polymerization iscarried out at a temperature of 70° C. in n-hexane (300 ml) with aAl(i-Bu) cocatalyst (3 mmole(1) at an ethylene pressure of 3 atm for 2hours. 0.007 g of catalyst is used to give 84 g of polyethylene. The PEyield is 12/kg PE/g catalyst or 480 kg/g Ti. The bulk density of the PEpowder is 0.38 g/cm³, the average PE particle size is 150 microns andthe SPAN value is 0.68. Polyethylene has an average viscosity molecularweight of 1.8·10⁶.

EXAMPLE 11

The catalyst produced in Example 6 is used for the polymerization ofethylene with hexene-1. Copolymerization is carried out at a temperatureof 70° C. in hexane (250 ml) with a Al(i-Bu)₃ cocatalyst (5 mmoles) 1 atan ethylene pressure of 2 atm and a hydrogen pressure of 0.25 atm, 10 mlof hexene-1 are charged into a reactor, the hexene-1/ethylene molarratio is 2.4.0.006 t of catalyst is used, the reaction is carried outfor 30 minutes to give 12 g of copolymer.

The catalyst activity is 4.0 kg/g catalyst.h or 200 kg/g Ti.h. Thecopolymer has a melt index MI₅ of 0.8 g/10 min and contains 4.5 mole %hexene-1.

Industrial applicability

The claimed method for preparing deposited catalysts for thepolymerization of ethylene and copolymerization or ethylene withδ-olefins will find applications to prepare catalysts, and catalystsproduced by the claimed method will find applications in solution,suspension and gas phase ethylene polymerization.

                                      TABLE                                       __________________________________________________________________________    Data on Ethylene Polymerization                                               Tit.       Activity  MI.sub.5                                                 Exp.                                                                             content,                                                                              Kg PE                                                                             Kg PE g   MI.sub.5.sup.2)                                                                     B · D..sup.5)                         No.                                                                              wt %                                                                              d avr.sup.1)                                                                      g cat · h                                                                g Ti (V) · h                                                               10 min                                                                            MI.sub.2                                                                         d.sub.30.sup.3)                                                                  g/cm.sup.3                                                                        SPAN.sup.4)                                __________________________________________________________________________    1  2.3 13.0                                                                              4.3 187   6.7 3.1                                                                              280                                                                              0.37                                                                              0.74                                       2  3.0 13.6                                                                              4.7 157   8.2 3.0                                                                              298                                                                              0.38                                                                              0.75                                       3  1.65                                                                              14.0                                                                              8.0 485   3.4 3.1                                                                              364                                                                              0.36                                                                              0.98                                       4  2.5 6.0 8.5 340   2.6 3.0                                                                              160                                                                              0.36                                                                              0.65                                       5  5.3 10.0                                                                              10.0                                                                              189   6.3 3.1                                                                              280                                                                              0.36                                                                              0.75                                       6  2.0 18.8                                                                              5.0 250   2.8 3.0                                                                              415                                                                              0.39                                                                              1.0                                        7  1.7 38.0                                                                              2.8 165   5.6 3.2                                                                              690                                                                              0.36                                                                              0.78                                       8  2.3 20.0                                                                              2.7.sup.6)                                                                        118   1.4 4.5                                                                              364                                                                              0.36                                                                              0.71                                       9  2.1 37.0                                                                              3.2.sup.6)                                                                        152   0.7 4.7                                                                              710                                                                              0.38                                                                              0.73                                       __________________________________________________________________________     .sup.1) average catalyst particle size                                        .sup.2) Polymer melt index ratio at loads of 5 kg and 2.16 kg which           indicate polyethylene molecular weight distribution                           .sup.3) average PE particle size                                              .sup.4) SPAN value indicates width of PE particle size distribution           .sup.5) PE bulk density                                                       .sup.6) Polymerization at ethylene pressure of 7.5 atm, hydrogen pressure     of 0.5 atm for 1 hour                                                    

We claim:
 1. A method of producing a deposited catalyst for thepolymerization of ethylene and copolymerization of ethylene withδ-olefins which comprises reacting a solution of an organomagnesiumcompound with an organic halide and subsequently treating the resultingcarrier with titanium or vanadium compounds, characterized in that theorganomagnesium compound is a product of composition MgPh₂.nMgCl₂.mR₂ O(wherein n=0.37-0.7; m≧2; R₂ O is an ether; Ph is phenyl) which isreacted with an organic halide at an organic halide to magnesium molarratio of ≧0.5 and at temperatures of -20° C. to 60° C.
 2. The methodaccording to claim 1, characterized in that the organomagnesium compoundis produced by reacting metallic magnesium with chlorobenzene in thepresence of dibutyl or diisoamyl ether.
 3. The method according to claim1, characterized in that the organic halide is carbon tetrachloride.